It seems like $this->getFinder()->getIterator() can also be of type array<integer,object<Sym...nt\Finder\SplFileInfo>>. However, the property $iterator is declared as type object<Iterator>. Maybe add an additional type check?

Our type inference engine has found a suspicous assignment of a value to a property.
This check raises an issue when a value that can be of a mixed type is assigned to
a property that is type hinted more strictly.

For example, imagine you have a variable $accountId that can either hold an
Id object or false (if there is no account id yet). Your code now assigns that
value to the id property of an instance of the Account class. This class
holds a proper account, so the id value must no longer be false.

Either this assignment is in error or a type check should be added for that assignment.